The work proposes to develop qualitative indices of early circulatory failure by the following steps: 1. Inducing congestive failure in a number of experimental animals. 2. Taking a series of chest radiographs on each animal as the condition progresses. 3. Processing and analyzing selected areas on the radiographs so as to produce measures of the animal's circulatory performance. 4. Simultaneously with the radiographic exposures record physiologic measures known to describe the cardiac and circulatory state. 5. Show the correlation of optical and physiologic measures and thereby demonstrate the validity of the non-invasive techniques to correctly assess the true state of early cardiac failures.